1. Technical Field
This invention relates generally to avionic sensor systems. Many aspects relate to an onboard system suitable for detecting obstacles and alerting the pilot during low-altitude, nighttime, helicopter operations.
2. Background Information
Low-altitude, nighttime, helicopter operations provide great advantages in many battlefield settings, but they also greatly increase the risk of collision with wires, cables, towers, antennae, trees, and terrain features. To augment pilot vision, the helicopter commonly includes imaging devices such as forward-looking infrared scanners (FLIRs) and image intensifiers (night-vision goggles). However, resolution often proves inadequate at normal flight speeds for timely detection of wires, steel towers, and other thin objects. That limitation can significantly impair operations and force reduced speed during transitional flight in which the pilot flies to a target at altitudes below 50 feet and during nap-of-the-earth flight in which the pilot flies as low as possible to avoid detection. Daytime operations also have obstacle-related problems. Thus, helicopter operations need a better way to detect obstacles.
Some prior attempts at wire detection employ radio waves in the millimeter wave band or light from carbon dioxide (CO.sub.2) lasers at 10.6 micrometers, Nd:Yag lasers at 1.06 micrometers, and various laser diodes at 0.85 micrometer. But none have led to the development of a small, compact, lightweight, cost effective obstacle avoidance system for aircraft. Such a system should also feature eye-safe operation for overflown personnel as well as aircraft ground crews, provide an effective pilot interface, and install conveniently in existing aircraft. Furthermore, it should operate at day or night and under inclement weather conditions, and it should not impair aircraft survivability.